A two-phase composition comprising a continuous phase thermoplastic material and a disperse phase elastomer, produced by dynamically vulcanizing the elastomer while the disperse phase elastomer is dispersed in the continuous phase thermoplastic material, is disclosed and known, for example, in Coran et al. U.S. Pat. Nos. 4,348,502, 4,130,535, 4,173,556, 4,207,404 and 4,409,365.
A fluorocarbon resin or a fluorine-containing elastomer is excellent in the heat resistance, and a two-phase blend obtainable by a combination of these materials, is expected to be excellent in the heat resistance. Such a fluorine-containing two-phase blend is disclosed in EP168020A. The elastomer used here is substantially a vinylidene fluoride/hexafluoropropylene elastomer, and as its vulcanization method, polyol vulcanization by a combination of bisphenol AF, an acid-receiving agent and an onium salt, or peroxide vulcanization by a combination of an organic peroxide and a polyfunctional unsaturated compound, is employed.
However, by such a vulcanization system, it takes a long time to completely vulcanize the fluorine-containing elastomer, and it is necessary to conduct oven vulcanization after the dynamic vulcanization, and there has been a problem that by the dynamic vulcanization only, the mechanical properties tend to be inadequate, particularly the permanent strain tends to be substantial, due to inadequate vulcanization of the elastomer in the composition.